94 PHOTO INTERPRETATION PICTURE, COLWELL 
“timelapse” photography taken from smaller telescopes (Kopal, 1959) which intioduces 
an entirely new concept of photo interpretation by which the roughness, steepness and 
general configuration of a surface is estimated from the rate at which shadows cast by 
surrounding tall objects are observed to move across it; and some from photographs 
taken from man-made satellites. 
  
Fig.2. An example of the use of terrestrial photography to document events 
that most people would consider to be quite unbelievable. Shown here is à 
rattlesnake of normal size engaged in devouring a full-grown jack rabbit. 
From detailed interpretation of sequential photography if this type, the 
rate and other characteristies of the process can be determined in detail. 
This represents one of the many new kinds of photo interpretation cur- 
rently being performed. (Photo courtesy U.S. Fish and Wildlife Service.) 
6. The importance of terrestrial photo interpretation is rapidly increasing. 
Figure 2 shows the value of terrestrial photographs, when properly interpreted, to 
document events that most people would not consider possible. In this illustration a rat- 
tlesnake of ordinary size is seen to be devouring a full-grown jack rabbit which it previ- 
ously had bitten and killed. From a series of such photos, carefully taken so as not to 
disturb Nature’s process, and then carefully interpreted, the rate of the process can be 
measured and a detailed analysis of the manner in which this phenomenon takes place 
can be accurately made. 
Figure 3 shows the value of sequential terrestrial photography for determining the 
rate at which a glacier is receding. 
7. The value of multiband spectral reconnaissance is gradually being recognized. 
Some photo interpretation problems which are insoluble through the use of any single 
film-filter combination can be solved quite readily when two or more such combinations